Amylases are an important group of carbohydrases and have an extensive industrial use. They are characterized by the ability to hydrolyze the alpha-D-glucosidic linkage in starch compounds and commercially their principal outlet is in starch processing technology. Starch, which is a polysaccharide of considerable molecular weight may be hydrolyzed by means of an alpha-amylase to produce polysaccharides of lower molecular weight containing up to ten monosaccharide units. Such an enzyme is termed a "liquefying" enzyme since, by cleaving the starch molecule, it converts to liquid form a starch suspension or a thick starch paste. Other amylases catalyze different hydrolytic operations, for example, beta-amylase catalyzes hydrolysis at the nonreducing ends of starch, glycogen or dextrin molecules splitting off a maltose molecule while glucoamylase catalyzes the removal of glucose from the nonreducing ends of the same poly- or oligo-saccharides.
Enzymes exhibiting alpha-amylase activity are obtained from a variety of natural sources, e.g., from molds, fungi and bacteria and enzymes from different organisms although having alpha-amylase activity and being able to catalyze the hydrolytic reactions catalyzed in general by alpha-amylases frequently differ in the conditions under which they operate, particularly, conditions of temperature and pH and in industrial practice, such differences may be important.
In U.S. Pat. No. 4,469,791 is described inter alia, a process for producing enzymes with amylase activity from genetically-engineered microorganisms. A number of microorganisms are described in that patent which donate to the genetically-engineered microorganisms genes coding for a variety of enzymes which show amylase activity. One such donor microorganism disclosed in U.S. Pat. No. 4,469,791 is B. megaterium (Bacillus megaterium) although the enzyme produced from this microorganism is not described as having any properties which would single it out from other enzymes with amylase activity described as being capable of being produced by the process of the patent. We have now found, however, that the enzyme from B. megaterium which has alpha-amylase activity, possesses properties which make it of particular use in certain industrial applications.